The confusing task of spot metering...

I always see people talking about 'metering' in articles. I knew that there were four metering settings on my camera (evaluative, spot, partial and centre weight)but I just usually leave it on evaluative which is the 'auto' setting. Generally metering is the way to find the best exposure but the evaluative one doesn't always find it.
I had a read various articles about the other types of metering and decided that spot metering looked quite handy for certain situations such as those where the subject is dark in a back-lit situation. At first I thought it was going to be simple: spot meter on most important part of the subject to take the exposure, press the auto exposure lock (AEL) to keep that exposure, recompose and take the shot with the stored exposure. If the exposure isn't right do the above again, but take the reading of the exposure from a different source.
So I headed outside with Massimo the cat so replicate the scene used in one of the articles I read...two kids, backs to the sun, kids came out too dark, he took a reading off one of the kids faces, took the photo again and wallah! The photo was perfect.
Unfortunately it didn't seem to want to work for me...



This first picture of Massimo was taken using the 'auto' evaluative meter. Looks pretty good, not too over or under exposed in full sunlight.




Then I moved around into a spot where it was shady but the sun was back-lighting the picture. I tried the same thing and it did this (above) and it also did the same for spot metering off anything that gave a reading of more than 1/640. The aperture was f8 and ISO was 400 for all the pictures.




For readings around 1/500 or less this is what it looked like. Massimo is fine but the background is way too overexposed.

I tried adjusting the exposure compensation and still nothing.


So how do you get a picture of a subject that is at the right exposure with the background good too? Hmm... looks like I might need to do a bit more research on that.

Next I went into a fully shaded area. The aperture was still f8 and the ISO was still 400. I took a photo of a flower...





The initial picture was taken with a reading from the flower of 1/125. That was slightly dark. I looked at the histogram and the peak was to the left indicating that it was under exposed(the peak should be in the middle).




This one was taken with a reading from one of the light green flower pods and was 1/500. It too was underexposed with the histogram showing even more to the left.




The next was taken from a different part of the garden from a darker spot which was metered at 1/40. It came out relatively well and the histogram says that the peak is slightly to the left but nearer the middle. It looks almost overexposed to me though.




And the final one was metered at 1/8 and was taken from the dark dirt. It is way too overexposed and the histogram is off the richter scale over to the right.

SO..what have we learnt? Readings off LIGHT things = a darker picture and readings off DARK things = a lighter picture. In other words a higher reading eg: 1/500 = a darker picture and vice versa. SO you have to find the average.

Or just use the evaluative meter.

Some sites about metering...
Spot metering used in different shots
A detailed description on spot metering
Exposure
Using a grey card to get a reading
Metering modes